This invention relates to an apparatus for controlling movement of a throttle valve in response to a change in the position of an accelerator pedal.
In order to meter the amount of mixture to an internal combustion engine, a variable positionable throttle valve is situated within the induction passage of the engine. Normally, a mechanical link mechanism is provided to couple the throttle valve to an accelerator pedal in a manner to move the throttle valve in response to movement of the accelerator pedal. If the throttle valve closes at a high speed to its idle position during deceleration, the intake-manifold negative pressure would increase to an excessive extent causing an intake air density reduction and a great amount of fuel collected on the intake passage walls being evaporated and drawn into the combustion chambers so as to create an over-rich fuel-air mixture, resulting in increased HC emissions, engine misfire, after-burning, and torque fluctuations which are a source of uncomforatable torsional vibration of the engine.
It is conventional practice to slow down the speed of closing movement of the throttle valve by using a mechanical dashpot device to retard closing of the throttle valve when the throttle valve position is at an angle less than a predetermined value. With such a mechanical dashpot device, however, attachment errors affect the angle at which the dashpot device starts retarding closing of the throttle valve, resulting in inaccurate throttle valve control.
Therefore, the present invention provides an improved throttle valve control apparatus which can control throttle valve closing movement with greater accuracy.